In modern engine technology, turbochargers are powered by the hot exhaust gas from the engine. It is desirable to convey the hot exhaust gas from the engine to the turbocharger in as high a temperature state as is possible. Some engine applications may make use of the exhaust's thermal heat. Recovery of the engine's wasted exhaust gas thermal heat may be used for warming residential living, factory assembly spaces, and the like depending on engine application. Recovery of the thermal heat is typically desirable at high heat rejection temperatures to allow for a more compact cooling system design. It is also desirable to maintain the temperature of the exhaust manifold below a predetermined temperature, such as below 750 degrees C. Prior techniques provide water jackets disposed about exhaust manifolds to reduce the temperature of the manifold. Unfortunately, the use of water jackets reduces the temperature of the exhaust gas, thereby reducing the energy supplied to the turbocharger and also the temperature of recoverable heat energy.
Some attempts have been made to produce a manifold with temperatures within allowable limits and, at the same time, to maintain the temperature of the exhaust gas as high as possible. One such system provides a sleeve inside the manifold which is surrounded by an air space. The air space provides insulation for the hot exhaust gas to keep their temperature as high as possible and, at the same time, to reduce the amount of heat transmitted to the water of the water jacket. That system also provides for accommodating for the heat insulating sleeve increasing in diameter under the expansion caused by the hot exhaust gas. In addition, in at least one version of said prior device, the heat insulation sleeve is cast in place in the manifold which makes it almost impossible to replace the heat insulation sleeve when it deteriorates or fails.
Another device, insulation material is provided around a heat insulating sleeve and a specially designed sliding connection is provided between the sleeve and a tube extending from each exhaust port of the engine. These connections are complicated, expensive and substantially impossible to maintain and service.
In another device, heat insulation is provided between the inner sleeve and an intermediate sleeve, with the inner sleeve being capable of axial movement against specially designed collapsible gaskets located between adjoining ends of the sleeves.
Another device discloses a manifold wherein the outer shell of the manifold is made in two parts which parts are assembled around an inner shell of the manifold so as to form a water jacket for cooling the inner shell with no insulation being provided for the inner shell.
The present invention is directed to overcoming one or more of the problems as set forth above.